Adriamycin coated silica microspheres as labels for cancer biomarker alpha-fetoprotein detection

Adriamycin (ADM)-coated silica microspheres as a label for the sensitive detection of a cancer biomarker alpha-fetoprotein (AFP) was reported. Silica microspheres (SiO2 MSs) were employed as the carrier for the immobilization of gold nanoparticles (Au NPs), secondary antibody (Ab2) and ADM (denote: ADM@Au NPs@SiO2 MS/Ab2) as labels. In the presence of AFP, the labels were captured on the surface of the Au NP-reduced graphene oxide (rGO) (Au NP-rGO) nanocomposites to form a sandwich structure vs. the specific recognition of antibody-antigen. In a pH 7.4 phosphate buffer solution, a well-defined peak of ADM at about -0.70 V (vs. SCE) was recorded via differential pulse voltammetry, the peak intensity of which was related to the concentration of AFP. Under optimal experimental conditions, the immunoassay exhibited a wide linear range (0.5 pg mL-1 to 75 ng mL-1) and low limit of detection (0.17 pg mL-1). Further, the immunoassay was evaluated for serum samples, which gave satisfactory results.

Nanostructures for nonlabeled and labeled electrochemical immunosensors: Simultaneous electrochemical detection of cancer markers: A review

The simultaneous electrochemical determination of multiple tumor antigens has attracted a great deal of attention, which can effectively enhance the capability and accuracy of the analysis. Nanostructured materials mostly played a key major role in the electrochemical immunosensors fabrication and operation improvement. This review focused mainly on the protocols for using nanostructures to fabricate electrochemical (nonlabeled@label-free and labeled@sandwich-type) immunosensors. Furthermore, this review has also described the diverse classes of electroactive nanospecies which are a complementary part of any immunosensor that assists to reach the selectivity for the target antigen. Finally, the important analytical characteristics of the published immunosensors were discussed (electrochemical detection technique, linear range, and detection limit). Studies published between the years 2009-2018 have been included in this review.

A Fe3O4@Au-basedpseudo-homogeneous electrochemical immunosensor for AFP measurement using AFP antibody-GNPs-HRP as detection probe

In this study, a Fe₃O₄@Au-based pseudo-homogeneous electrochemical immunosensor was prepared for detection of alpha fetoprotein (AFP), a well-known hepatocellular carcinoma biomarker. The primary antibody (Ab1) was immobilized on Fe₃O₄@Au NPs as the capture probe. Horseradish peroxidase (HRP) and secondary antibody (Ab2) were conjugated on gold nanoparticles (GNPs) through electrostatic adsorption to form signal-amplifying labels. In the presence of AFP, a sandwich immunocomplex was formed via specific recognition of antigen-antibody in a Fe₃O₄@Au-basedpseudo-homogeneousreaction system. After the immunocomplex was captured to the surface of magnetic glassy carbon electrode (MGCE), the labeling HRP catalyzed the decomposition of H₂O₂, resulting in a substantial current for the quantitative detection of AFP. The amperometric (i-t) method was employed to record the response signal of the immunosensor based on the catalysis of the immobilized HRP toward the reduction of H₂O₂ with hydroquinone (HQ) as the redox mediator. Under the optimal conditions, the amperometric current response presented a linear relationship with AFP concentration over the range of 20 ng/mL-100 ng/mLwith a correlation coefficient of 0.9940, and the detection limit was 0.64 ng/mL at signal/noise [S/N] = 3. Moreover, the electrochemical immunosensor exhibited higher anti-interference ability, acceptable reproducibility and long-term stability for AFP detection.

Ultrasensitive non enzymatic multiple immunosensor for tumor markers detection by coupling DNA hybridization chain reaction with intercalated molecules

In this study, we tried coupling the small signal molecules that could intercalate into DNA double helix with hybridization chain reaction (HCR) technique to fabricate a multiple immunosensor. Doxorubicin hydrochloride (DXH) and methylene blue (MB) were used as signal molecules and alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) were selected as model biomarkers. The immunosensor mainly consists of three parts as follows: First, two different primary antibodies (Ab₁) immobilized on the surface of gold nanoparticles (Au NPs); Second, secondary antibodies (Ab₂) conjugated with DNA primer; Third, long DNA concatemers from HCR were used as a carrier to intercalate amounts of signal molecules (DXH or MB). A sandwich immunocomplex was formed among primary antibodies, target biomarkers and secondary antibodies conjugated with DNA primer via specific recognition reaction. Afterwards, DNA concatemers intercalating amounts of DXH or MB were linked to DNA primer via DNA hybridization. Square wave voltammetry (SWV) was employed to record the response signals from electroactive molecules DXH and MB, and two distinguishable signals were obtained, which peak potentials were at about -0.30V (corresponding to MB) and -0.70V (corresponding to DXH, both vs SCE), respectively. The signal intensities of MB and DXH were linearly related to the logarithm of biomarkers concentration in the range of 0.05pgmL^-1-25ngmL^-1, and the limit of detection were 0.03pgmL^-1 for CEA and 0.02pgmL^-1 for AFP (at S/N=3), respectively. Furthermore, the immunosensor exhibited a sensitive electrochemical response to biomarkers in human serum samples and the results obtained were in accordance with reference method, indicating the immunosensor can be applied to real sample analysis in clinic diagnosis.